1. Field of the Invention
The present invention relates to a laser beam machining method of very precisely machining a high-precision component such as a hologram or an ink-jet print head nozzle used in an ink-jet printer.
2. Description of the Related Art
By way of example, a conventional laser beam machining technique used to produce an ink-jet print head nozzle will be described below, although the technique also has various other applications in production of high-precision components. In recent years, as personal computers have come to be more and more widely used, ink-jet printers have also come to be widely used as a hard copy machine. Ink-jet print heads for use in ink-jet printers can generally be classified into three types. They are a resistance heating type in which ink is heated by means of resistance heating, an electric current heating type in which an electric current is passed directly through ink, and a piezoelectric type in which a voltage is applied to a piezoelectric element thereby inducing deformation in the piezoelectric element. These techniques will be described in further detail below.
In the resistance heating technique, heat is generated by passing a current through a resistance heater so that ink present in a region in direct contact with the heater is boiled by the generated heat thereby emitting ink through a nozzle and thus forming marks on paper or the like. In the technique in which a current is passed directly through ink, ink is boiled by the current flowing through the ink so that the ink is emitted through a nozzle thereby forming marks on paper or the like. In the print head based on the piezoelectric effect, mechanical vibrations are generated by applying a voltage to piezoelectric ceramic thereby emitting ink through a nozzle.
In any technique, it is required that a nozzle used in a print head have an optimized structure to achieve high performance in the operation of emitting ink and thus high quality in the printed characters or images.
The structure of the nozzle will be described in further detail below. In general, the nozzle includes: an orifice part having an opening through which ink is emitted; a channel through which ink passes; and an ink supplying part. Since the nozzle structure is an important factor in the ink emission performance, a great number of techniques in terms of the nozzle structure and production methods thereof have been developed and disclosed in patents. For example, Japanese Unexamined Patent Publication No. 7-164175 discloses a technique of forming a nozzle in a heat-resistant resin sheet using an excimer laser beam (excimer laser beam technique). Another technique is to produce a nozzle by means of nickel plating. This technique is known as the electroplating technique, and the nozzle produced by this technique are called electroplated nozzle. Although other techniques such as the technique of forming a nozzle using a stamper, the technique based on the injection molding, etc., are also known, the excimer laser beam technique and the electroplating technique are now widely used in practical production.
In the conventional technique of producing a nozzle using an excimer laser beam, separate various masks are prepared for an orifice part, an ink channel, and an ink supply part, and the orifice, the ink channel, and the ink supply part are produced in different processing steps using the corresponding masks. Thus, it is required to exchange the mask placed on an excimer laser machining system for each processing step.
As disclosed in the excimer laser beam machining technique disclosed in Japanese Unexamined Patent Publication No. 7-164175, it is known to use a mask covered with a reflecting film (semitransparent film) which changes in reflectance (transmittance) across the mask in accordance with the nozzle structure to be formed.